Applicants have discovered a process for enhancing the properties of boro-aluminosilicate EU-1 and related zeolite structures together with a catalyst based thereon having enhanced properties.
EU-1 is a high activity aluminosilicate zeolite catalyst (U.S. Pat. No. 4,537,754) having 10-ring pores and high internal volume. It is useful as a catalyst and sorbent and shows interesting shape selectivity (U.S. Pat. No. 4,537,754; Sovererijns et al, Microporous Materials, 4, page 123 (1995)). Its compositional variations include the replacement of Al by Ga, Fe or B. As the acidity of these different metal (M) forms decreases in the order Al, Ga, Fe, B, reactions requiring the lowest acidity, such as paraffin isomerization, are probably best carried out with the borosilicate form or those materials having high Si/M ratios (i.e., lower number of acid sites). Unfortunately, when made at the higher silica ratios (those greater than about 40) some EU-1 materials have poor sorption capacity after removal of the templates normally used in its synthesis) resulting in poor accessibility of reactants and low catalytic reactivity. This may be caused by partial framework collapse (reflected in deteriorating X-ray diffraction evidence) or trapped detrital material blocking the pores (indicated by stable X-ray diffraction profiles but inferior n-hexane sorption capacities). Evidence seems to point to the latter cause in these subject materials and may be inherent to the high silica synthesis process, which requires excess silica in the mother liquor, resulting in entrainment, primarily, of siliceous species within the zeolite structure. In constrained pore systems such as EU-1, a small amount of detritus may readily block major parts of the accessible structure. Whilst it is well known that post acid treatments or chemical treatments with complexing agents may restore structural accessibility in some zeolites, including EU-1, in this case, such treatments would tend to remove the framework boron, or other M entities, responsible for the desired selective catalytic activity.
The instant invention is directed to a process for selectively removing detrital material from boro-aluminosilicate selected from EUO, NES and intergrown mixtures of EUO and NES boro-aluminosilicate topology zeolites having a Si/M ratio of greater than about 50, comprising treating said boro-aluminosilicate with a base for a time and at a temperature sufficient to remove said detrital material from said boro-aluminosilicate wherein the concentration of said base is less than about 0.5 normal. Base concentrations in excess of this level may cause the removal of framework components leading to subsequent structural degradation.
The invention is likewise especially directed to boro-aluminosilicates selected from EUO, NES and intergrown mixtures of EUO and NES boro-alumino-silicate topology specifically boro-alumino-slicate EU-1, said boro-aluminosilicate prepared by treating a boro-aluminosilicate containing detrital material with a base for a time and at a temperature sufficient to remove said detrital material from said boro-aluminosilicate wherein said boro-alumino silicate has a Si/M ratio of greater than about 50.
The above boro-alumino silicates have improved wax isomerization properties.